1. Field of the Invention
This invention relates to data processing systems. More particularly, this invention relates to performance counters in data processing systems.
2. Description of the Prior Art
In order to monitor and/or control the performance level within a data processing system it is desirable to have a performance counter. It is known to provide performance counters that count the number of processing cycles executed by a processor. Such performance counters do not readily combine with information concerning real time as the count rate will vary with the processing clock speed selected without a ready indication of whether a desired amount of processing has been done within a desired amount of time.
It is also known to provide real time clocks which operate by steadily incrementing a count value under control of a fixed clock frequency to keep track of the passage of time. Such real time clocks do not provide an indication of the number of processing cycles that may or may not have been performed in a given period of time dependent upon the particular clock frequency for the processor being used at that time.
It would be desirable to provide a performance counter that was able to take account of different processing clock signals that may be selected at different times and yet provide real time based performance information.